What do you want to migrate? Existing virtual machines?
–
GerrySep 26 '12 at 11:28

If you want to migrate existing VMs, this will depend on the operating system running inside them. On the surface it's just moving/converting the disk images, but you're likely to run into driver problems with some OSes.
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pmdjSep 26 '12 at 12:11

Yep, exactly. I would like to move my Win7 installation from Parallels to VB.
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EnrichmanSep 26 '12 at 12:35